package Udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
   private DatagramSocket socket = null;
   public UdpEchoServer(int port) throws SocketException{
       socket = new DatagramSocket(port);
   }
   public void start() throws IOException {
       System.out.println("服务器启动");
       while(true) {
           DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
           //1.读取请求并解析
           socket.receive(requestPacket);
           String request = new String(requestPacket.getData(),0,requestPacket.getLength());
           //2.根据请求计算响应
           String response = this.process(request);
           //3.把响应写回客户端
           DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),0,response.getBytes().length,
                   requestPacket.getSocketAddress());//此处为 获取客户端地址
           socket.send(responsePacket);
           System.out.printf("%s %d req=%s,res=%s\n",responsePacket.getAddress(),requestPacket.getPort(),request,response);
       }
   }
   private String process(String response) {
       return response;
   }

    public static void main(String[] args) throws IOException{
        UdpEchoServer server = new UdpEchoServer(9098);
        server.start();
    }
}
